In the article the results of studies conducted regarding the thermal processing of rape straw, rye straw and willow chips applying various parameters of the pyrolysis process are presented. Samples of biomass were subject to thermal processing at various temperatures and process durations, assessing the impact of the applied conditions on physicochemical parameters of the obtained pyrolysis products. The contents of phosphorus, potassium, magnesium, carbon and nitrogen were analysed. The studies have indicated that the pyrolysis process can be used to refine biomass, among others obtained from straw and chips, in the context of using it for fertilization. Modification of the pyrolysis process parameters (temperature, time) significantly impacted the concentration of the analysed macroelements. It has been stated that the highest content of phosphorus, potassium and magnesium in biocarbon (rape straw, rye straw and willow chips) can be obtained performing pyrolysis at the temperature of 5000C for 10 minutes. A significant impact of the pyrolysis parameters – temperature and time on the total content of macroelements in the obtained biocarbon was observed. The highest contents of phosphorus, potassium and magnesium were observed in the case of biocarbon obtained at the temperature of 5000C during 10 minutes, while the temperature of 4000C and duration of 10 minutes allowed to obtain the maximum content of carbon and nitrogen.